Sextant

A sextant is an instrument generally used to measure
the altitude of a celestial object above the horizon.
Making this measurement is known as "sighting the object,"
"shooting the object," or "taking a sight." The angle, and
the time when it was measured, can be used to calculate
a position line on a nautical or aeronautical chart. A
common use of the sextant is to sight the sun at noon
to find one's latitude. Held sideways instead of upright,
the sextant can be used to measure the angle between any
two objects, such as between two lighthouses, which will,
similarly, allow for calculation of a line of position
on a chart.